ZEMCH 2019 International Conference Proceedings April.2020 | Page 377
The turbulence model used was the K‐Epsilon model, the most common turbulence model, where
k is the turbulent kinetic energy and ε is the dissipation rate of turbulent energy. This model is based
on the time‐averaged Navier–Stokes equations, which assumes that the time‐varying velocities of
turbulence can be divided into time‐averaged velocities and velocity‐dependent velocities. Therefore,
the model itself is simple, which is advantageous in terms of calculation convergence [8].
Table 2. Simulation conditions for air‐type PVT collector
Boundary condition parameter
Turbulent model
Heat flux
PV area (LxH)
Fluid
Inlet, Outlet area of collector
Air in (temperature)
Air out
Air density
Buoyancy
Gravity
Free convection to environment
Value
k ‐ ε model
700W/m 2 on the PV surface
1.54m 2 (1,011x1,520mm)
Air
0.0344m 2
67m3/h (7 °C)
Pressure Outlet
1.225kg/m 3
Application
9.81m/s 2
Application
3. Analysis of simulation results
3.1 Heat Transfer Performance
Figure 2 shows the flow velocity distribution with or without baffle inside air‐type PVT collector.
Based on the results, the baffle‐free collector length increased to the outlet without stagnation. The
collector with baffle (Case 3) tended to have a weak local flow rate at the back of the baffle, but the flow
rate was significantly faster in the space between the baffles. Therefore, compared with the reference
collector, the internal flow rate of the collector with the baffle was faster and the outlet flow rate
increased.
Figure 3 shows the temperature distribution with or without baffle inside air‐type PVT collector.
For collector in Case 3, the air temperature rose due to the locally low flow rate on the back of the baffle,
but the space between the top of the baffle and the back of the PV was narrow, causing the air to sweep
away quickly. Therefore, it can be seen that the air did not stagnate locally on the back of the baffle and
passed quickly to the outlet. As a result, the collector having the baffle had a faster outlet flow rate and
a higher outlet temperature than the reference collector, so the former’s heat transfer performance was
advantageous.
Figure 2. Velocity distribution with or without baffles inside air‐type PVT collector
Comparative Analysis for Improvement Thermal Performance of
Air-type PVT Collector with Triangular Baffles
366